In the prior art there exists a deficiency in the methods and devices used in the introduction of a hypodermic needle into venous or arterial blood vessels of humans and animals. Often times the person administering the syringe needle will penetrate through the blood vessel or miss the blood vessel altogether. Such mishaps can cause severe agitation and pain to patients. The problem even persists among trained phlebotomists. The problem occurs more often where the blood vessels are difficult to see or palpate under tissues. In such areas discerning the depth and position of the blood vessel becomes even more difficult. Additionally, positioning of the blood vessel may be misjudged because blood vessels tend to move as the needle advances. Indeed, even experienced phlebotomists often miss the vessel or just stab through it.
Devices in the prior art have been used to enhance needles to provide needle tip position relative to a blood vessel. One such device is the xe2x80x9cSmart Needlexe2x80x9d. The xe2x80x9cSmart Needlexe2x80x9d utilizes an ultrasonic doppler probe placed within the tubular needle bore such that some reflectance cuing of the needle tip position relative to a blood vessel wall is provided to the operator. A drawback of the xe2x80x9cSmart Needlexe2x80x9d is that lumen definition is not provided. Due to its size the Smart Needle is limited to the relatively large diameter of needle gauges 18 to 22. The present invention is able to attain a gauge size 30 which is sufficiently narrow to treat pediatric or veterinary subjects. Additionally, the indicating means unit of the Smart Needle is relatively large and must be connected to the penetrating means via a five foot long coaxial cable. The one-time use only needles costs $70.00 per needle unit in packs often each.
Other devices in the prior art distinguish between adipose and muscle tissues or vascular transition. One such device is described in U.S. Pat. No. 5,271,413 entitled Method to Sense the Tissue for Injection from a Hypodermic Needle. The device described in the aforementioned patent utilizes bioimpedance to define the transition between adipose and muscle tissues or vascular transition. These devices aid in the introduction of drug agents into specific tissues enabling proper tissue absorption. These devices do not address blood vessel structures and are not capable of discriminating, proximity locating, or lumen defining. The device and method described in the ""413 Patent uses an electrode positioned on the skin surface and the needle to introduce a signal into the body and detect the impedance with the reference electrode. These measurements are then used to determine the type of tissue in which the needle is currently located. Accurate results require the reference electrode to be placed some distance from the needle target area and the needle to penetrate into the tissue 2 to 5 millimeters.
One embodiment according to the invention is a hypodermic needle having an end that attaches to a syringe and an elongated hollow shaft for passing fluid terminated at a sharpened point; the improvement comprising an electrically insulating layer positioned on the shaft and at least one electrically conductive area positioned on said insulating layer; said electrically conductive area being adapted to be connected to an electrical source.
A method according to the invention is a method of determining when a hypodermic needle penetrates into tissue, vein, or lumen. The method comprises providing a hypodermic needle having two electrically conducting portions, spaced apart from each other, and near a point on the hypodermic needle, and electrically insulated from each other. The conducting portions being adapted to be connected to an electrical source to enable electrical current to flow through said conducting portions. Next, determining the change in the electrical current between the conducting portions when the hypodermic needle is penetrating a conductive body. Finally, generating a visual and/or audible signal indicating when the conducting portions have penetrated the conductive body and reached a predetermined position.
Yet another embodiment of the invention is a system for determining when a hypodermic needle penetrates into tissue, vein, or lumen. The system comprising a hypodermic needle having two electrically conducting portions, spaced apart from each other, and near a point on the hypodermic needle, and electrically insulated from each other. The conducting portions being adapted to be connected to an electrical source to enable electrical current to flow through them. An electrical source electrically connected to the conducting portions. A means for determining the change in the electrical current between said conducting portions when the hypodermic needle is penetrating a body and a signaling means for generating a visual and/or audible signal indicating when the conducting portions have penetrated the body and reached a predetermined position.